Conventional aircraft employ large numbers of incandescent filament bulbs, many within the aircraft cabin. Examples of such incandescent filament bulbs are the reading lights that are located above most, if not all, seats within the cabin. These incandescent filament bulbs not only consume relatively large amounts of power but also generate relatively large amounts of heat. This contributes to the fuel expenses for an aircraft operator because not only must fuel be consumed to generate the power needed to illuminate the bulbs, but fuel must also be consumed to generate the air conditioning needed to cool the cabin to a comfortable level to accommodate the heat generated by those bulbs. Moreover, the operating life of an incandescent filament bulb is noticeably less than other lighting alternatives, such as light-emitting diodes (LEDs). Thus, the use of incandescent filament bulbs within aircraft also contributes to the maintenance costs for operating the aircraft because the incandescent filament bulbs will need replacement relatively often.
Therefore, the inventor herein discloses a need in the art to improve aircraft fuel efficiency and maintenance costs through replacement of an aircraft's incandescent filament lamps with LEDs. However, simply swapping out an aircraft's incandescent filament bulbs for LEDs is problematic. Airplanes, particularly commercial airliners, generally employ sophisticated monitoring systems that run diagnostic checks on the operational status of various aircraft components, including the incandescent filament bulbs located in the cabin. These legacy monitoring systems are configured to expect that incandescent filament bulbs be used in the reading lamps (and flight attendant call lights), and the monitoring system's circuitry and software is configured accordingly. That is, the monitoring system is configured to perform tests on the aircraft lamps wherein these tests are geared to an expectation that the lamps use incandescent filament bulbs.
To these monitoring systems, operational incandescent filament bulbs present themselves as relatively low resistance loads. If there is a break in the filament (or some other problem), non-operational incandescent filament bulbs present themselves to the monitoring systems as relatively high resistance loads. It is this difference is resistance levels that most monitoring systems detect in order to assess whether aircraft lamps are operational.
However, relative to an incandescent filament bulb, an LED arrangement exhibits a higher resistance. Thus, if an incandescent filament bulb were simply replaced with an LED arrangement, the relatively higher resistance exhibited by the LED arrangement would register as a fault with the monitoring system, thus preventing deployment of the LED arrangement.
In an effort to solve this problem in the art, the inventor herein discloses an LED circuit assembly comprising a filament bulb simulation circuit in combination with an LED load, the filament bulb simulation circuit being configured to simulate the load that would be presented to a monitoring system by a filament bulb. In this way, the monitoring system does not register a fault when an operational LED is used to replace an incandescent filament bulb, thereby permitting effective deployment of LEDs to replace the aircraft's incandescent filament bulbs. Preferably, the filament bulb simulation circuit is deployed in parallel with the LED load.
In a preferred embodiment, the filament bulb simulation circuit comprises a capacitor in parallel with the LED load. In one embodiment, the capacitor is sized such that the LED circuit assembly exhibits an equivalent series resistance that simulates the resistance that the monitoring system expects to see from an operational incandescent filament bulb. In another embodiment, the capacitor is sized such that the LED circuit assembly exhibits a capacitive reactance that the monitoring system expects to see from an operational incandescent filament bulb.
Thus, in a preferred embodiment, the LED circuit assembly is configured to work in connection with an aircraft's legacy monitoring system, thereby allowing replacement of an aircraft's incandescent filament bulbs with LEDs without also modifying the aircraft's monitoring system. Further still, the LED circuit assembly is preferably configured for deployment in legacy sockets within the aircraft, thus avoiding the need to retroactively alter the sockets within an aircraft that are already fitted for receiving incandescent filament bulbs. In this way, the cost of replacing an aircraft's energy inefficient incandescent filament bulbs with LEDs is greatly reduced.
Furthermore, because of the low amounts of heat that are generated by a preferred embodiment of the LED circuit assembly, the LED circuit assembly preferably does not employ a heat sink, thereby providing the preferred LED circuit assembly with weight savings that also contribute the aircraft's fuel efficiency.
Further still, the LED circuit assembly preferably comprises a voltage converter circuit connected between the LED load and the filament bulb simulation circuit. In instances where the LED circuit assembly received an AC voltage input, the voltage converter circuit preferably comprises a rectifier bridge circuit.
These and other features and advantages of the present invention will be apparent to those having ordinary skill in the art upon review of the following description and drawings.